These house rules are intended to fix two problems I percieve with level draining creatures, while level draining is a serious and lasting consequence it doesn't leave an interesting mark and secondly level draining creatures reproduce too easily with wraiths creating wraiths etc.
The house rule:
When level drained, in addition to losing a level, a character gains a Wraith-level. Wraith-levels represent corruption of the spirit and when a creature with Wraith-levels die their spirits rise as incorporeal malevolent undead in D4-1 days. What type of undead they become depends on the number of Wraith-levels they had. In addition, if the number of Wraith-levels ever exceed the number of ordinary levels that characters spirit leaves their body as a malevolent spirit of the appropriate type each night and attempts to murder an innocent. Should the malevolent spirit be slain that character dies with no possibility of resurrection. Wraith-levels can only be removed through a Wish spell.
Wraith-levels brings creatures closer to the spirit world in thought, perception and being. Wraith-levels grant living creatures certain advantages.
Able to "Hear" undead with Hear Noise
Your unarmed attacks count as magic weapons
Immune to non-silver or non-magic weapons
% In Lair: 35%
Dungeon Enc: Sorrow (1d8) / Gallery (1d3 Sorrows)
Wilderness Enc: Gallery (1d3 Sorrows) / Lamentation (2d10 Galleries)
Movement: 90' (30')
Armor Class: 2
Hit Dice: 1**
Attacks: 1 (paralyzing touch)
Damage: 1d4 + Paralysis (may roll each rouch to break free)
Treasure Type: B (per Gallery)
Ghasts appear as semi-solid spirits uttering their last death-rattle as they haunt the living. Their touch is immensely cold and paralytic in the short term unless a save vs Paralysis is made. Paralyzed characters may roll save vs. Paralysis again at the start of each round and if they succeed they are immune to the paralysis of Ghasts for the remainder of that round. Ghasts are resistant to damage taking 1 point of damage from attacks not from silver, magic or magic weapons. Large groups of ghasts are often accompanied by a more powerful undead creature which was responsible for their creation. For each Gallery there is a 20% chance of a more powerful undead being present. Roll to see which kind: 1-3 Wight, 4-5 Wraith, 6 Spectre. Ghasts have the usual undead immunities to poison, charm, hold and sleep spells.
Why post this?
I need help coming up with the quirks of Revenants as well are more benefits from Wraith-levels (or at what levels they kick in to make it balanced).
The Fiend Folio from 1st edition had a revenant. Basically an 8 HD undead that can't be turned, having all the abilities it had in life. It was immune to all (normal and magic) weapons, and rarely spoke unless casting spells it knew in life. It had one purpose - kill the person who killed it. It would wrap its hands around the targets neck for 2d8 damage until victim was dead. The limbs could continue to work even if severed and it regenerated. The only way to kill it was turn it to ash.
This is cool. True to ACKS uniqueness I might allow time spent in a pinnacle of good (illuminated, hallowed, sacrosanct as per the upcoming Heroic Companion) to remove wraith levels just as it removes corruption.
So the strength of an undead spawn is based on the level of the creature whose levels are being drained rather than on that of the undead? That would prevent rapid reproduction of high-level creatures... But it also means that almost any undead can produce other creatures that're unrelated to the original in every way save for both being undead. That means throwing away some of the existing lore and flavour of (for example) vampire reproduction... Do you have an in-setting explanation for why undead can produce otherwise-unrelated undead to replace it?
What happens if you wake up a sleeping person while their spirit is wandering the night in search of an innocent life? Does the spirit get dragged back to the body, howling with frustration? Or does the person simply become impossible to wake? (If the latter, what effect does moving the body while the spirit is away have on the spirit's ability to return to the body?)
Can a person remember (however vaguely) what their wandering spirit did during the night? Can they influence or direct their spirit's actions so as to (for example) assassinate specific people they don't like in waking life rather than people at random?
Why does killing someone's spirit when they were alive prevent them from being ressurected when killing it once they're dead has no such effect?
The wraith corruption really seems like something that higher level characters would actually want to get, just for the benefits. Provided they keep their level above their corruption it seems like they essentially get bonuses for free. Especially appealing to those classes of a darker bent, or those that will eventually become undead anyway.
You may want to add a downside to these along with the bonus. Maybe they heal slower (say 1-2 point less healing per corruption level, be it from naturally healing or from magic), or have other quirks that make life more complicated in general.
@GMJoe good questions. I imagine the spirit actually being the corrupt soul of the person, it would find its way back unless magically obscured somehow (or blocked) in which case the body doesn't wake. Or if we go with the metaphysics of ACKS all the way it might way and start generating a new soul from its life processes. I would allow a player to direct their soul if they had a good idea, but since it murders innocents I'd imagine most worthy targets don't qualify.
As for reproduction, there is still the necromantic transformation and other processes. I think Wraiths and Vampires can auto-generate from either sins commited during life or a great need for vengeane or similar. I think the Vampires presented in the books is just one flavor of blood sucker, the rabies like infection vampire is another kind of being. Being able to generate 7HD creatures out of 0th level humans seems like a way to build a cheap unstoppable army quickly.
@Loswraith I think the major drawback is not being able to die in peace and the 25% risk of rising as an undead instantly each time you die. If you get 0 days on the roll you rise right away so there is no chance of restoring the body before the evil spirit pops out. Wraith levels should probably provide a penalty to Tampering with Mortality. As for the boons I don't think they're balanced which is why I started this thread for advice.
A classic undead trait is the unease of animals around you (exception for vampires and their wolves, bats and rats of course). Perhaps a subtration to reaction roles for any natuaral animal for every level of corruption. This could also apply to celestials (if you have such a thing in your campaign world).